Menstrual Cycle Patterns and Their Determinants during the Menopausal Transition among a Multiethnic Cohort of Women.

Abstract

Examining menstrual cycle patterns among early and mid-reproductive aged women suggests that ethnicity, body mass index (BMI), and medical conditions influence menstrual characteristics. Little data is available on bleeding patterns and dysfunction during the menopausal transition. The few studies conducted among perimenopausal women include predominately Caucasian populations and did not examine factors that may alter bleeding patterns during the menopausal transition. The aim of this dissertation was to examine patterns of change in menstrual cycle characteristics during the menopausal transition using menstrual calendar data from a multiethnic multisite cohort study, the Study of Women’s Health Across the Nation (SWAN). Monthly menstrual calendars were recorded between 1996 -2006. This dissertation found that staging the menopausal transition by menstrual calendars identified the start of each menopausal stage than with estimates from annual interviews. Increase in menstrual cycle length occurred predominately in the right tail of the distribution, with greater variability in extreme lengths occurring during the 2 years prior to the final menstrual period (FMP). Menses of 10 or more days, menses with at least 6 days of spotting, and menses with at least 3 days of heavy bleeding occurred at least once during the menopausal transition in the majority of women. Menses of 15 or more days were less common. Obese women had longer menstrual cycle lengths and were more likely to report menses with at least 3 days of heavy bleeding. After adjusting for body size, Chinese and Japanese women had longer menstrual cycle lengths and Japanese women were less likely to report menses with at least 3 days of heavy bleeding. African-American women were less likely to report menses of 10 or more days or menses with at least 6 days of spotting. Menstrual characteristics were not associated with diabetes, thyroid conditions, or uterine fibroids after adjustment. The normative patterns of menstrual cycle characteristics as women progress through the menopausal transition include increased propensity for longer menstrual cycles, longer-lighter menses, and episodes of heavy menstrual bleeding. The results of this work will help define abnormal uterine bleeding in perimenopausal women.